1. Field of the invention
The present invention relates to vapor phase deposition apparatus and a vapor phase deposition method. For example, a mechanism which condition a flow of a raw gas containing a silicon source used in the manufacturing of a wafer in an epitaxial growth apparatus.
2. Related art
In the manufacturing of a semiconductor device such as an ultrahigh-speed bipolar transistor or an ultrahigh-speed CMOS, an epitaxial growth technique for a monocrystal in which an impurity concentration and a film thickness are controlled is indispensable to improvement of performance of a semiconductor device.
In epitaxial growth which refines a monocrystal thin film on a wafer or the like, an atmospheric-pressure chemical vapor deposition method is generally used. Depending on circumstances, a low-pressure chemical vapor deposition (LPCVD) method is used. A wafer is set in a vapor phase deposition reaction furnace. A state in the vapor phase deposition reaction furnace is kept at an atmospheric pressure (0.1 Mpa (760 Torr)) or a vacuum atmosphere of a predetermined degree of vacuum, and a raw gas obtained by mixing a silicon source and a dopant such as a boron compound, an arsenic compound, or a phosphorous compound is supplied into the furnace while the wafer is heated and rotated. A thermal decomposition or a hydrogen reduction reaction of the raw gas is performed on a surface of the heated wafer to grow a vapor phase deposition film doped with boron (B), phosphorous (P), or arsenic (As), thereby manufacturing a epitaxial wafer.
The epitaxial growth technique is also used in the manufacturing, for example, an IGBT (Insulate Gate Bipolar Transistor). In order to manufacture a high-performance semiconductor device, a high-quality crystal film is required to be uniformly and thickly grown. For example, only a film thickness of several micromillimeters or less is necessary in a simple MOS device or the like. However, in an IGBT or the like, a film thickness of several micromillimeters to one hundred and several score micromillimeters is necessary. For this reason, the wafer is rotated at a high speed, and a raw gas is caused to flow onto a wafer surface heated to a vapor phase deposition temperature. A newly supplied raw gas is sequentially brought into contact with wafer surfaces to grow vapor phase deposition films on the wafer surfaces. In this manner, a growth rate of the vapor phase deposition film is advanced.
FIG. 9 is a conceptual diagram showing a configuration of a conventional vapor phase deposition apparatus 400.
When conventional vapor phase deposition is performed, a wafer 401 is held on a holder 404 (also called a susceptor). The wafer 401 is rotated at a high speed with the holder 404 rotated at a high speed. The wafer 401 is heated by using an inner heater 405 and an outer heater 406. A raw gas is supplied from a supply passage 407 connected to a chamber 402. The raw gas is thermally decomposed or hydrogen-reduction on the wafer 401 to grow a vapor phase deposition film.
In this case, concerning a technique to grow a vapor phase deposition film with a uniform film thickness distribution, a technique of performing vapor phase deposition while rotating a wafer at a high speed is disclosed (for example, see Published Unexamined Japanese Patent Application Publication No. 5-152207(JP-A-05-152207)).
However, even though a center of gravity of the placed wafer 401 is slightly out of a center of rotation of the holder 404, the wafer 401 disadvantageously gets out of the holder 404 in response to centrifugal force or the like generated by high-speed rotation of the holder 404. In the worst case, both the vapor-deposition deposition apparatus 400 and the wafer 401 may be broken by the blown-off wafer 401.